Network management applications often need to know, for a given type of event on a given connection, a variety of network performance items including the total number of events that occur during the connection, the number of times that the event occurrences reach some threshold value (threshold crossing), how often this is occurring, and other information. The invention has the ability to perform these and other functions in a novel manner that conforms with OSI standards.
Event counting is well known in various arts. For example, in the telephone switching art, it has been a common practice for many years to accumulate "peg" counts of the utilization of switching office resources as well as the number of trouble reports reported by the resources. Such peg counts are typically used to estimate the adequacy of the resources for handling call loads, especially during busy hour traffic. Event counting is also known in the computing art. U.S. Pat. No. 3,906,454 describes a computer monitoring system for detecting, filtering and storing both hardware and software events. The system is geared toward a debugging system, whereby system information can be gathered without interrupting the operation of the computer system, thereby avoiding a source of system distortion that can render test results less useful. Event and error counting is also common in the networking art, for example to assess the level of transmission quality of the various network connections between nodes and users. Typical known techniques for networks include accumulation of total error counts during a connection and the measuring of the duration of the connection; counting until a threshold is reached, irrespective of how long it takes to reach the threshold and counting to a threshold, thereafter followed by variations on the thresholds and timing intervals intended to discover bursty, but transient conditions, and actual degraded connections that should be retired.
In U.S. Pat. No. 4,080,589, the occurrence of an error triggers a timer and begins a counting interval. Subsequent errors occurring during the interval are counted until a predetermined threshold is reached or the timing interval expires. If the threshold is reached before expiration of the interval, an alarm is signaled and the timer is reset to begin a new interval. Each subsequent error resets the timer until a complete error free interval occurs.
In U.S. Pat. No. 4,241,445, a time base circuit measures recurrent intervals T2; each T2 contains an intermediate interval T1. A first error counter counts errors up to a threshold during intervals equal at most to T2 and at a minimum to T1. A second error counter counts each threshold crossing of the first counter. The second counter signals an alarm when it reaches a predetermined value.
In U.S. Pat. No. 4,291,403, if an error count exceeds a predetermined threshold during an established time period, an alarm is generated and a second threshold is established to measure subsequent error rates.
U.S. Pat. No. 4,339,657 establishes a variable time interval measured by a predetermined number of operations that occur. The arrangement counts errors occurring during the operations and also counts the number of times that the error count crosses a predetermined threshold.
U.S. Pat. No. 4,800,562 is said to provide a continuous indication of data quality in a data stream. A first counter counts periodic events in a data stream. A second counter counts errors in the data stream. When the first counter overflows, it recycles and also resets the second counter. When the second counter overflows, it recycles and resets the first counter. If the error rate is low in relation to the periodic events, the first counter will prevent the second counter from overflowing. An overflow of the second counter indicates an excessive error condition.
Other background art is described in U.S. Pat. Nos. 4,363,123 and 4,291,403.
While the known art is satisfactory in specific instances, the art does not provide sufficient flexibility for today's standards. Techniques are needed that enable the accumulation of information that can be manipulated to provide a variety of measurements, while at the same time being efficient and simple to implement.